再探早期示例
时间:2007-05-29 yycnet.yeah.net yyc译
为注意到一些利用新事件模型的例子和为学习程序从老到新事件模型改变的方法，下面的例子回到在本章第一部分利用事件模型来证明的一些争议。另外，每个程序包括程序片和应用程序现在都可以借助或不借助浏览器来运行。1. 文本字段这个例子同TextField1.java相似，但它增加了显然额外的行为：
//: TextNew.java
// Text fields with Java 1.1 events
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class TextNew extends Applet {
Button
b1 = new Button("Get Text"),
b2 = new Button("Set Text");
TextField
t1 = new TextField(30),
t2 = new TextField(30),
t3 = new TextField(30);
String s = new String();
public void init() {
b1.addActionListener(new B1());
b2.addActionListener(new B2());
t1.addTextListener(new T1());
t1.addActionListener(new T1A());
t1.addKeyListener(new T1K());
add(b1);
add(b2);
add(t1);
add(t2);
add(t3);
}
class T1 implements TextListener {
public void textValueChanged(TextEvent e) {
t2.setText(t1.getText());
}
}
class T1A implements ActionListener {
private int count = 0;
public void actionPerformed(ActionEvent e) {
t3.setText("t1 Action Event " + count++);
}
}
class T1K extends KeyAdapter {
public void keyTyped(KeyEvent e) {
String ts = t1.getText();
if(e.getKeyChar() ==
KeyEvent.VK_BACK_SPACE) {
// Ensure it''s not empty:
if( ts.length() > 0) {
ts = ts.substring(0, ts.length() - 1);
t1.setText(ts);
}
}
else
t1.setText(
t1.getText() +
Character.toUpperCase(
e.getKeyChar()));
t1.setCaretPosition(
t1.getText().length());
// Stop regular character from appearing:
e.consume();
}
}
class B1 implements ActionListener {
public void actionPerformed(ActionEvent e) {
s = t1.getSelectedText();
if(s.length() == 0) s = t1.getText();
t1.setEditable(true);
}
}
class B2 implements ActionListener {
public void actionPerformed(ActionEvent e) {
t1.setText("Inserted by Button 2: " + s);
t1.setEditable(false);
}
}
public static void main(String[] args) {
TextNew applet = new TextNew();
Frame aFrame = new Frame("TextNew");
aFrame.addWindowListener(
new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
aFrame.add(applet, BorderLayout.CENTER);
aFrame.setSize(300,200);
applet.init();
applet.start();
aFrame.setVisible(true);
}
} ///:~
当TextField t1的动作接收器被激活时，TextField t3就是一个需要报告的场所。我们注意到仅当我们按下“enter”键时，动作接收器才会为“TextField”所激活。TextField t1附有几个接收器。T1接收器从t1复制所有文字到t2，强制所有字符串转换成大写。我们会发现这两个工作同是进行的，并且如果我 |
